We have owned our 2015 for two years now - got her used from a family member with about 55k miles. The car is comfortable, fast, huge, and gets great mileage for its size and weight - about 21mpg with a mix of city of highway miles and I'm shocked by that. This is the year they put the 3.0 liter twin turbo V6 in the GL450 - not sure what other years they did, but I highly recommend this engine. V6's are often marketed as having V8 power when they really don't, but this one absolutely has V8 power. It even sounds like a V8. You can certainly feel the car's heft on turns in country roads, but it weighs basically 3 tons fully loaded. It feels very safe and is super quiet inside - build quality is superb. It feels like a fast, luxury tank. I love it and I'm going to drive it as long as I possibly can.

The 2015 GL550 turbo is off the rails. Push the sport mode button and some kind of witchcraft happens. It is a fast, comfortable brute that puts many 2023 SUVs to shame. Highway, no problem, B roads, no problem, snow, no problem, heavy rain, no problem. It does it all. Mine was 110K new. I picked mine up used for 40 with 35K on the clock. I use mine like an SUV. We hunt, fish, and put the dogs in the back. It does it all. Do not take your Merc to the dealer. Some folks specialize in Merc and will do your routine maintenance for thousands less. Yes, thousands less. Some of which you can do yourself. I'm on a Mercedes forum. Folks help you with countless features. The Germans know what they are doing.

Owned a newer 2014 S-Class, but we could never get two golf bags in the trunk. It was a beautiful and lots of technology but needed more cargo volume. Bought a 2015 GL450 pre-owned from the local Mercedes dealership. The newer GLS is more expensive and feels less solidly built and tons of electronics that can go wrong. Overall, I am happy with the comfort and utility of this SUV. We took it on a couple road trips in its first year. I have distronic plus radar cruise control and didn't know that it also helps automatically stop to avoid a collision. Some crazy driver stopped in the middle of a highway trying to get into a left lane and I would have rear ended them if I didn't have the radar with the active brake assist. The comand navigation screen is smaller than on the newer ones and the night time backup view is too dark. I've had some glitchy performance with the Comand system, but it's a 7 year old SUV, but it's somewhat to be expected. Overall, great SUV to live with for at least the next 5-10 years before everything goes electric.